On the jacking tabs I tried to find what I could on these and see what Ford actually called them. The official name for them is "Plate, Front Suspension Lower Arm". So they were not called jacking tabs, but thats been the common name for years everyone has been using.
One thing that seems for sure is the owner was not expected to crawl under the car and put the trunk jack under there to raise the car. So if these were used for jacking purposes it would have been with a floor jack or a shop lift.
As far as the shape of them cant say for sure why they had different shapes. Makes more sense to me that the square tabs came on the earlier cars like Bob is saying especially since the drawing I attached in my first post here shows the rounded style with a C6 engineering number.